The invention relates generally to multi-wall structural components that are capable of enhancing the transmission of incident radiation. Further, the invention relates to methods for forming the multi-wall structural components.
Various types of plastic sheet structures made of plastics, such as polycarbonate or acrylic resins are known and commercially available. Such sheets can be obtained in a transparent or a translucent form for use in a variety of applications. The transparent or translucent plastic sheets have been combined in different ways to form multi-wall sheet structures that are used for applications, such as for roof, window, vertical wall glazing, and the like, where there is a need for light to be transmitted. In general, when radiation falls on a surface, some combination of reflection, transmission, and absorption occurs. When visible light falls on a plastic surface, the absorption of the light by the plastic is negligible and therefore only reflection and transmission modes are considered. Therefore, if “R” denotes the percentage of amplitude of the electric vector in the reflected light, the percentage of amplitude of the electric vector in the transmitted light will essentially be (100-R). The reflection of visible light incident on a transparent surface can be given by Equation 1:R/E=(n cos φ′−cos φ)/(n cos φ′+cos φ)  (Equation 1)wherein “R” denote the amplitude of the electric vector in the reflected light, “n” is the refractive index of the transparent medium, “φ” is the angle of incidence, and φ′ is the angle of refraction. “E” denotes the amplitude of the electric vector in the incident light. At normal incidence, φ and φ′ become zero, and therefore the transmittance is given by Equation 2:R2/(E)2=((n−1)/(n+1))2  (Equation 2)wherein “R”, “E”, and “n” are as described previously. For normal incident light, it follows from Equation 2 that for a glass surface having a refractive index of 1.5, the value of reflectance at an air/glass interface is 0.08, or 8 percent of such incident light gets reflected. Typically, when solar radiation interacts with a plastic sheet at normal incidence, up to around 88 percent of light can be reflected due to air/plastic refractive index mismatch. This determines the maximum entitlement for transmission through the plastic sheet. In a multi-wall plastic sheet structure, since there is a plurality of air/plastic interfaces, the efficiency of light transmission is further reduced. It has been estimated that if light transmission through a multi-wall sheet structure, such as for example, a green house roof can be increased by around 1 percent, the yield of the green house increases by around 5 percent. Further, in the case of industrial roofing, enhanced light transmission helps in daylight energy savings.
Therefore, there is a need for multi-wall sheet structures that not only have superior structural stiffness, but can also transmit an enhanced amount of an incident radiation, such as electromagnetic radiation or visible radiation.